We shall strive more particularly in this document to describe the problems and issues existing in the context of radiocommunications terminals that have to switch from one first network enabling access to telematic applications towards a second network enabling access to an emergency call service. The present disclosure is naturally not limited to this particular context of application but is of interest for any switching technique that must cope with similar or proximate problems and issues.
Such radiocommunications terminals traditionally have a first connection profile associated with a first radiocommunications network and a second connection profile associated with a second radiocommunications network. Each connection profile comprises all the data enabling the terminal to get connected, i.e. to get synchronized and register, with the network with which it is associated, this data being an identifier for connection to the network, international mobile subscriber identity (IMSI) number, the synchronization frequency band associated with the network, an authentication key, associated algorithms for authenticating the subscriber on the network, etc.
Typically, both connection profiles can be stored on one detachable card inserted in the radiocommunications terminal, for example a SIM card (Subscriber Identity Module), an ICC (Integrated Circuit Card), an IUCC (Universal Integrated Circuit Card) or an R-UIM (Removable User Identity Module) card, or else the two cards can be stored on two distinct detachable cards each being dedicated to the storage of one of the two connection profiles. Thus, when the terminal must switch to a radiocommunications network, this network gets physically connected either to the detachable card containing all the connection profiles or to the detachable card storing the connection profile relating to the network to which the terminal must switch, in order to extract therefrom the data needed for its synchronization and its registration.
The connection profiles can also be stored in a local memory integrated into the terminal or in a memory included in a remote equipment of the terminal such as for example a server having a storage memory and communicating with the terminal by means of a WiFi or Wimax radiocommunications system.
Here below the drawbacks of the prior art are discussed with reference to the particular case of a motorist whose vehicle has broken down or who has been in an accident, and wishes to make an emergency call.
In such a situation, the motorist can wish to use his mobile terminal, which is then connected to a present radiocommunications network (for example a telematic network compliant with the GSM standard) and may wish to switch it to a second radiocommunications network proposing access to an emergency call service.
The term “current network” refers to the radiocommunications network with which the terminal is connected, i.e. synchronized and registered (by the first network) and the term “substitution network” refers to the radiocommunications network to which the terminal must switch (the term used then is “second network”).
As illustrated in FIG. 1, the working of the current technique for switching can be summarized as follows:                step 1: the terminal receives a switching request which identifies the substitution network I towards which it must switch (this is the network providing access to an emergency call service here);        step 2: upon reception of the switching request, the terminal gets physically connected to the SIM card to extract therefrom the connection profile relating to the substitution network i;        step 3: the terminal reads the connection profile i as well as the associated information which will be used to implement the steps of synchronization and registration;        step 4: the terminal measures the reception power level of the beacon frequencies that it receives in scanning the entire frequency band determined from the extracted connection profile i, in order to get synchronized with the substitution network i;        step 5: once synchronized, the terminal gets registered with the substitution network i so that the terminal can switch to this network which then becomes the current radio telecommunications network;        step 6: once the terminal is connected to this network, the user of the mobile terminal make an emergency call on the network providing access to an emergency call service.        
When the terminal receives a new switching request, the steps 1 to 6 described here above are reiterated so that the terminal can switch from the current network to another substitution radiocommunications network.
The current switching technique however has several drawbacks. Indeed, the current switching process for switching from a first to a second radiocommunications network is relatively lengthy (typically more than 20 seconds for a GSM or UMTS network) since, whenever a switching is needed, it requires the implementation of a set of steps (extraction, reading, synchronization and registration) causing a loss of time before the connection to the network is made.
However, it is important in the context of a mobile communications, and especially emergency calls, that the switching from a terminal of a first communications network to a second radiocommunications network is done as speedily as possible in order to offer the user communications on the desired network within the best possible time limits.
Another known solution relies on the use of a DSDS (Dual SIM Dual Standby) type radiocommunications terminal. This type of terminal has two SIM cards, a first SIM card comprising a first connection profile associated with a first network, and a second SIM card comprising a second connection profile associated with a second network which can be activated simultaneously. This enables the simultaneous extraction of both connection profiles and the synchronization of the terminals simultaneously with both radiocommunications networks. When a call is made on one of the two networks via a SIM card, the other SIM card is made inactive, stopping the process of connection to the other network.
However, the “Dual SIM Dual Standby” method is based on a dual SIM card driver mechanism which is complex to implement since it requires, on the one hand, simultaneous access to two different SIM cards (and therefore the simultaneous activation of two different drivers) and, on the other hand, a management of two different radiocommunications protocols working at the same time.
The electronic card enabling execution of the embedded driving firmware is therefore relatively complex to implement and takes up substantial space which it is difficult to reduce.
Besides, another drawback of this dual SIM card driving mechanism is that it causes high-energy consumption. This prior-art solution is therefore not an optimal one.